The present invention relates generally to devices used to sequentially trim sheet material articles, and in particular to an infeed apparatus for a sheet material article trimmer.
A known apparatus for trimming sheet material articles, such as books, includes a front knife assembly which trims front edge portions of the books and a side knife assembly which trims side edge portions of the books. The front knife assembly includes a front table which moves a book while a front edge portion of the book is being trimmed by a front knife. Similarly, the side knife assembly includes a side table which moves the book as opposite side or head and tail edge portions of the book are trimmed by a pair of side knives.
An infeed pusher, or shuttle, pushes each of the books in turn onto the moving front knife table of the known apparatus. If the trimmer mechanism is exactly adjusted for the size of the books to be trimmed, the speed of movement of the infeed shuttle will match the speed of movement of the front knife table for the instant of time at which the leading edge or back of the book first engages backstops which register the book relative to the front knife. The infeed shuttle then moves out of engagement with the book. Shortly thereafter, a front clamp grips the book and holds it against movement relative to the front table.
The exact time when the front clamp engages the book is determined, at least in part, by the thickness of the book. Thus, the front clamp will grip a thick book before it grips a thin book. This is because the front clamp must move through a shorter distance to close against a thick book. Due to rebounding of the book from the backstops and/or closing of the front clamp either too soon or too late, the book may not be precisely positioned relative to the front table when the front edge is trimmed by the known apparatus. Of course, this is detrimental to the quality of the front trim.
The above-described known apparatus for trimming books or other sheet material articles is disclosed in U.S. Pat. No. 3,733,947 issued May 22, 1973 and entitled “Book Trimming Machine”. An apparatus for trimming books and other sheet material articles and constructed as disclosed in this patent has been commercially available from Harris Graphics, a division of AM International, of 4900 Webster Street, Dayton, Ohio 45414 and is referred to as the HT-15 Trimmer.